Central Christchurch property owners opposed to the Government's plans to acquire their land are trying to slow down the acquisition process by refusing to supply critical information on their properties.

The Christchurch Central Development Unit has sent letters to more than 800 central-city property owners on its intention to acquire their land and asking them to fill out a detailed questionnaire about their property, including the status of any insurance claims.

The unit plans to use that information to help determine the value of the property, but some property owners say the unit is asking for confidential information that their legal advisers do not believe should be made available at this stage.

So far the unit has received only 54 of the 884 questionnaires it sent out.

Denis Harwood, a long-term property investor who owns three sites in the city centre that the Government wants to buy, said he had been advised not to complete the questionnaire and was aware of many others who had been given similar advice.

Harwood said most property owners were unhappy with the acquisition process and felt it was "theft by rezoning".

According to Harwood, the unit said it would pay market value for the properties, but it was using data from a handful of "fire sales" made after the quakes to determine market value.

Some owners believed those sales did not accurately reflect market values or the investment people had made in their properties.

"All this just flies in the face of [Canterbury Earthquake Recovery Minister] Gerry Brownlee and [Prime Minister John] Key's statements that people would not lose their equity," he said.

City Owners Rebuild Equity chairman Ernest Duval said he had heard that many property owners were refusing to fill out the insurance portion of the questionnaire because they felt the Government should be talking to them directly, not to their insurers.

"People are nervous about how this situation may be approached and there is still a lot of uncertainty out there because the scale of the land acquisition is something that is totally unprecedented."

One of the many unanswered questions was whether landowners would be reimbursed for the make-safe work they had been forced to do on their properties after the quakes or for the work on drawing up plans for the redevelopment of their sites.

"People need to take professional advice because it really is uncharted territory," Duval said.